The goal of this project will be to develop an interdisciplinary network of scientists dedicated to measuring biological risk for late life health outcomes in large representative samples of populations. Biological risk is defined by indictors of physiological state that increase the probability of disease, disability, loss of physical or cognitive functioning, or death. The network will focus on assessing, harmonizing and validating biological risk measurement in populations; expanding measures available for use in populations; and developing methodological approaches for including complex dimensions of health in analytic models. Scientists who will co-direct the network represent the disciplines of epidemiology and demography with named Core network participants in biology, genetics, psychology, economics and medicine. Members of the network will eventually include investigators from most of the major population studies in the U.S. and a number of international studies, researchers in relevant areas, and emerging scholars. Proposed subgroups of the network include measurement and validation, genetics, life-long effects, and innovation. Activities of the network will include designing and carrying out a series of focused meetings, regular conference calls, workshops, and pilot projects to harmonize and develop measurement. The network will develop multiple approaches to the dissemination of modules on collection methods, assay methods, basic training on relevant topics, and analytic methods. Dissemination of harmonizing information will be a major product of the network. The network will promote interdisciplinary, interuniversity, and international research on factors affecting health outcomes common in old age in large community and national population surveys. This is an emerging area of scientific focus in the population sciences which is at an ideal stage of development to benefit from an organized network. RELEVANCE (See instructions): Biological risk represents objective measurement of major dimensions of population health. The level of risk can indicate the health of the population, need for health care treatment in a population, and the effectiveness of that treatment in controlling risk or delaying disease progression, and death. The measurement of biological risk in large populations often requires adoption of methods not used in laboratory settings. This project will improve the methods of measuring health used in populations and improve comparability of results over time and across studies which is important for monitoring population health.